This invention relates to fuel controls for turbine types of power plants and particularly to the power lever and associated indexing adjustment mechanism and the method of the setting thereof.
The typical fuel control for a turbine type power plant such as the JFC-12, JFC-25, JFC-60 and the like, manufactured by the Hamilton Standard Divison of United Aircraft Corporation, the assignee hereof, includes a power lever that when installed on the engine and ultimately to the power lever in the aircraft cockpit to be manipulated by the pilot requires a tedious and sometimes cumbersome installation procedure. (The cockpit power level and the power lever on the fuel control are words of art and each are connected to each other in the aircraft and act in unison). Notwithstanding the fact that the heretofore known fuel control is calibrated at the factory prior to shipment, when installed on the aircraft it is usually re-set in order to match its linkage to the linkage on the aircraft. This marriage of linkage usually occurs in order to adjust for tolerances both in the aircraft linkage and fuel control. It is abundantly important that when the pilot adjusts his power lever to a particular position the fuel control, through its linkages, cams and mechanical connections will produce a given response and will deliver the correct amount of fuel corresponding to this setting.
In the heretofore known fuel controls, as those mentioned above, the typical installation included a power lever cover mounted on the fuel control casing, an index plate keyed to the power lever shaft having a bifurcated or slotted portion extending over the cover adapted to be aligned with arcuately spaced holes and a micro adjusting ring. The power lever cover is movable relative to the casing, the index plate is movable relative to the power lever and power lever cover, and the micro ring is movable relative to the power lever and index plate. In other words, all the above mentioned parts are movable relative to each other and their orientation relative to space and relative to the working parts within the fuel control housing has to be set mechanically with the aid of flow meters and/or test rigs. A better understanding of the prior art control will be discussed in connection with the description of the preferred embodiment presented hereinbelow.
I have found that I can simplify the indexing of the power lever of the fuel control, facilitate its installation in the aircraft, and elimate its micro adjusting ring, the bifurcated or slotted portion on the index plate and its cooperating aligning holes. By virtue of this invention a factory calibrated control can be mounted on the aircraft, fitted to the complementary adaptor without requiring any further adjustments. According to this invention an aligned dowel and slot and a predetermined aligned position of the power lever shaft relative to the dowel and slot, are provided to accept a complementary adaptor mounted in the aircraft that connects to the power lever mounted in the cockpit. This invention provides maximum angular accuracy without binding of the mechanism.